Yet that doesn't make the decision on who to back any simpler for Democrat voters.

The pair are polling closely and it came down to a coin toss to decide who came out on top in the Iowa caucus at the beginning on February.

While Clinton remains the overall favorite to win the Democratic nomination, Sanders is keen to show that his campaign can give the former secretary of state a run for her money deep into election season.

So where do Clinton and Sanders align, and where do they clash over key issues like healthcare, the economy and foreign policy?